Vehicle braking system

ABSTRACT

Rotatable road wheels of a vehicle are associated with fluidoperated brakes and with pressure-exerting brake-operating means for operating the brakes. An anti-blocking system is provided between the brakes and the brake-operating means and has a sensor which senses the revolutions of the road wheels, an electromagnetic valve controlled by the sensor and able to switch on and off a source of compressed air, a control valve which controls the flow of brake fluid to the brakes and which is movable between an open and a closed position, and a reducing piston which switches the control valve between its positions and which is movable in a sense switching the control valve to closed position under the influence of pressure fluid from the compressed air source, and in a sense switching the control valve to open position under the influence of pressure exerted by the brake-operating means.

United States Patent [1 1 Von Lewis et al.

VEHICLE BRAKING SYSTEM Inventors: Alexander Von Lowis, Mauren; JosefTrui, Bissingen, both of Germany Assignee: Robert Bosch GmbH, Stuttgart,

Germany Filed: Aug. 5, 1971 Appl. No.: 169,335

Foreign Application Priority Data Aug. 13, 1970 Germany P 20 40 206.6

References Cited UNITED STATES PATENTS 5/1972 Williams 303/21 F 11/197]Horvath 303/21 F Aug. 28, 1973 Primary Examiner-Duane A. RegerAttorney--Michael S. Striker [57] ABSTRACT Rotatable road wheels of avehicle are associated with fluid-operated brakes and withpressure-exerting brake-operating means for operating the brakes. Ananti-blocking system is provided between the brakes and thebrake-operating means and has a sensor which senses the revolutions ofthe road wheels, an electromagnetic valve controlled by the sensor andable to switch on and ofi a source of compressed air, a control valvewhich controls the flow of brake fluid to the brakes and which ismovable between an open and a closed position, and a reducing pistonwhich switches the control valve between its positions and which ismovable in a sense switching the control valve to closed position underthe influence of pressure fluid from the compressed air source, and in asense switching the control valve to open position under the influenceof pressure exerted by the brake-operating means.

4 Claims, 2 Drawing Figures Patented Aug. 28, 1973 3,754,795

2 Sheets-Sheet l NVENTOR a 0 {14 W355: V: U 00:!

VEHICLE BRAKING SYSTEM BACKGROUND OF THE INVENTION I The presentinvention relates generally to a vehicle, and more particularly to avehicle having road wheels. Still more particularly the inventionrelates to a vehicle braking system and, in particular, to a vehiclehaving a braking system provided with an anti-blocking arrangement.

From German Gebrauchsmuster 6,906,118 it is already known to provide avehicle with a brake system having an anti-blocking device. In thissystem the wheels are associated with brakes which in turn are providedwith a connection to a brake-operating means. Interposed between thebrake operating means and the brake is an anti-blocking arrangementcontrolled via a sensor by the rotation of the wheels. The anti-blockingdevice has an electromagnetic valve which is influenced by the sensor, acontrol valve which supervises the flow of brake fluid through the brakeline, and a reducing piston which switches the control valve and whichis influenced, in a sense closing the control valve, by the pressurederived from a pressure source which is switched into the system .by themagnetic valve when the latter is operated. While the system justmentioned is operative it is to be noted that the reducing piston isacted upon only one-sidedly by varying pressure. This means that arelatively long response time is required so that short response times,which are of course desirable in anti-blocking devices, cannot beachieved.

SUMMARY OF THE INVENTION It is, accordingly, an object of the presentinvention to avoid the disadvantages of the prior art.

More particularly it is an object of thepresent invention to provide animproved vehicle braking system having an anti-blocking device whichresponds and switches much more rapidly than what is known from the art.1

A concomitant object is to provide such a system and such a device whichis simple in its construction.

In pursuance of the above objects, and of others which will becomeapparent hereafter, one feature of the invention resides in a vehiclewhich, briefly stated, comprises rotatable road wheels andfluid-operated brake means for breaking the rotation of the road wheels.Pressure-exerting brake-operating means is associated with the brakemeans and anti-blockingmeans is interposed between the brake means andthe brakeoperating means. The anti-blocking means comprises sensingmeans which senses the revolutions of the road wheels, electromagneticvalve means controlled by the sensing means, control valve meanscontrolling the flow of fluid to the brake means and movable between anopen and a closed position, a source of pressure fluid connectable withthe control valve means by operation of the electromagnetic valve means,and a reducing piston which switches the control valve means and ismovable in a sense switching the control valve means to closed positionunder the influence of pressure fluid from the source, and in a senseswitching the control valve means to open position under the influenceof pressure from the brake-operating means. I

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however,

both as to its construction and its method of operation, together withadditional objects and advantages thereof, will be best understood fromthe following description of specific embodiments when read inconnection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERREDEMBODIMENTS Discussing firstly FIG. 1 it will be seen that the vehiclebraking system illustrated therein is provided with a brake valve 1which may also be considered a brakeoperating means; it is connectedwith a supply container 2 for compressed air. An air conduit 3 connectsthe valve 1 with an auxiliary cylinder via a branch 6, and via anadditional branch 12 with the inlet 13 of an anti-blocking device 4. Theauxiliary cylinder is identitied with reference numeral 7, and ahydraulic line 8 connects it with the inlet 9 of the unit 4. Theauxiliary cylinder 7 is constructed as a pressure-translating devicehaving a pneumatic piston 10 which is influenced by pressure in the airconduit 6, and which is mechanically connected with a smallerhydraulicpiston 11.

Located in and constituting a part of the unit 4 is a switching valve 14which utilizes a valve seat 14'' cooperating with a ball-shaped valvemember 14'. Beneath the valve 14 is located a hydraulic piston 15 whichcan act upon the valve 14 via a rod 15' and which is fixedly connectedwith a larger compressed-air operated reducing piston 16 via a rod 15".Beneath the piston 16 is provided a chamber 17 with which the inlet 13communicates, and a chamber 18 is above the piston 16 and connected witha magnetic valve 20 via a conduit 19. The magnetic valve 20 supervisesrespective connections of the chamber 18 with an atmospheric-airconnection 21 and with a supply container 22. It is pointed out that thecontainers 2 and 22 may either be supplied with one and the same(not'illustrated) source of compressed air, for instance a compressor,or they may be supplied by individual sources or alternately thecontainers 2 and 22 may be replaced by a single container.

A connection 23 intermediate the valve 14 and the piston 15 connects thehydraulic brake line 8 with the road wheel brakes 24. The road wheelsare shown for purposes of illustration, as is a sensor which cooperates'with the magnetic valve 20.

In operation of the braking system, and assuming that a braking incidentis being initiated, the brake valve '1 is operated and compressed airfrom container 2 flows via the conduit 3 and 6 to the auxiliary cylinder7, and.

via the conduit 3 and 12 to the chamber 17 of the unit 4. This causesthe compressed air to act upon the piston 16 which latter is pushedupwardly so that the hydraulic piston 15 displaces via the rod 15' thevalve 14 to open position. Via the thus-opened conn'ol valve 14 thehydraulic brake pressure, which is translated by the auxiliary piston 7,enters into the brake line 8 to act upon vehicle brakes 24 so that thewheels are now braked.

Assuming, now, that one of the wheels becomes blocked during suchbraking, then the magnetic valve 20 is energized via thediagrammatically illustrated sensor (which may be of known type such asthat disclosed in the aforementioned prior-art German Gebrauchsmuster)and the valve 20 thus becomes displaced from the illustrated switchingposition into its other switching position. As a result of thiscompressed air from the container 22 can flow into the chamber 18displacing the piston 16 downwardly and causing the piston with rod 15to participate in such movement. This effects movement of the controlvalve 14 to closed position and the hydraulic pressure in the brake line8-- which is located behind the valve 14is reduced. The blocked wheel isnow released again and can resume turning, which is sensed by the sensorwhereupon the latter de-energizes the magnetic valve 20.

It will be appreciated that the present invention assures a very rapidresponse of the unit 4 by utilizing compressed-air counterpressure atthe piston 16. Furthermore, an additional advantage over what is knownfrom the prior art is that a biasing spring in the chamber 17 is avoidedin the construction according to the present invention, and that asource of error is eliminated which previously resulted from the use ofsuch biasing springs where the strong forces acting upon such a springin the case of pressure reduction-which occurs in rapid sequence in suchunits-can easily lead to a breakage of the spring and to malfunction.

The embodiment of FIG. 2 is basically constructed along the same linesas that in FIG. 1, and the same reference numerals have been utilized todesignate like elements. In this embodiment, however, a loaddependentpressure-limiting device 30 is interposed in the conduit 3 and 12 whichoriginates at the valve 1, meaning that in addition to the operationwhich is described above with respect to the system of FIG. 1, theembodiment according to FIG. 2 has the possibility of load-dependentbraking force limitation. In operation of the system illustrated in FIG.2, braking causes above the piston 15 the brake pressure whichis-supplied to the brakes 24, and in the chamber 17 beneath the piston16 the load-dependently reduced brake pressure, so that the valve 14will move between its open and closed positions (that is change itsswitching position) at a low brake pressure, meaning that the brakepressure is load-dependently reduced. If in the system of FIG. 2 thedevice or unit 4 becomes activated as a result of blockage of a roadwheel, then the brake pressure is further reduced until the wheel willagain turn. After the magnetic valve is subsequently de-energized, thebrake pressure supplied to the brakes 24 is again regulated in aload-dependent sense. This regulation takes place analogously to aninterception control, meaning that the pressure level determined by theloaddependent pressure-limiting device 30 is not exceeded. Of course itwill be appreciated that a simple pressurelimiting device can be used,instead of a loaddependent device 30, and in this case a single one willbe adequate for each wheel axle.

An additional advantage of the embodiment of FIG. 2 is the fact that ifthe brake pressure supplied by the valve 1 and controlled by the device30 beneath the piston I6 is so limited in its level that in case of fullbraking the critical pressure ratio (p reducing pistonl6)/(p container22) 0.528 is not exceeded, then the compressed air will enter out of thecontainer 22 with the speed of sound whereby shortest possibleregulating times are achieved even at very small brake pressure in thebrake line, a consideration which is particularly important in certaincircumstances, for instance if the vehicle suddenly moves from a dryroad onto an iced road.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in avehicle brake system, it is not intended to be limited to the detailsshown, since various modification and structural changes withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art fairly constitute essentialfeatures of the generic or specific aspects of this invention and,therefore, such adaptations should and are intended to be comprehendedwithin the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent isset forth in the appended claims:

1. In a vehicle having a source of pressure fluid, in combination,rotatable road wheels; fluid-operated brake means for braking therotation of said road wheels; pressure exerting brake-operating meansassociated with said brake means; anti-blocking means interposed betweensaid brake means and brakeoperating means said anti-blocking meanscomprising sensing means sensing the revolutions of said road wheels,valve means controlling the flow of fluid to said brake means,and beingmovable between an open and a closed position, electro-magnetic valvemeans controlled by said sensing means and operative for connecting saidsource of pressure fluid with said control valve means, and a reducingpiston switching said control valve means, and being movable in a senseswitching said control valve means. to closed position under theinfluence of pressure fluid from said source, and in a sense switchingsaid control valve means to open position under the influence ofpressure from said brakeoperating means; brake line means connectingsaid brake operating means with said anti-blocking means and the latterwith said brake means; and a pneumatically operated cylinder-and-pistonunit interposed in said brake line means intermediate said brakeoperating means and said anti-blocking means and receiving from theformer fluid the same fluid as said reducing piston receives from saidsource.

2. In a vehicle as defined in claim 1, further comprising a regulatingvalve for adjusting the pressure which acts upon said reducing pistonfrom said brakeoperating means.

3. In a vehicle as defined in claim 1, wherein said cylinder-and-pistonunit is a hydraulic unit.

4. In a vehicle as defined in claim 1, wherein said fluid supplied bysaid source is pressurized air.

1. In a vehicle having a source of pressure fluid, in combination,rotatable road wheels; fluid-operated brake means for braking therotation of said road wheels; pressure exerting brake-operating meansassociated with said brake means; antiblocking means interposed betweensaid brake means and brakeoperating means said anti-blocking meanscomprising sensing means sensing the revolutions of said road wheels,valve means controlling the flow of fluid to said brake means,and beingmovable between an open and a closed position, electro-magnetic valvemeans controlled by said sensing means and operative for connecting saidsource of pressure fluid with said control valve means, and a reducingpiston switching said control valve means, and being movable in a senseswitching said control valve means to closed position under theinfluence of pressure fluid from said source, and in a sense switchingsaid control valve means to open position under the influence ofpressure from said brakeoperating means; brake line means connectingsaid brake operating means with said anti-blocking means and the latterwith said brake means; and a pneumatically operated cylinder-and-pistonunit interposed in said brake line means intermediate saidbrakeoperating means and said anti-blocking means and receiving from theformer fluid the same fluid as said reducing piston receives from saidsource.
 2. In a vehicle as defined in claim 1, further comprising aregulating valve for adjusting the pressure which acts upon saidreducing piston from said brake-operating means.
 3. In a vehicle asdefined in claim 1, wherein said cylinder-and-piston unit is a hydraulicunit.
 4. In a vehicle as defined in claim 1, wherein said fluid suppliedby said source is pressurized air.